The present invention relates to an apparatus and method for fabricating cylinders from multi-ply flexible web material having outer thermo-plastic plies sandwiching a central metallic ply. More particularly, the type of flexible cylinder which the present invention is designed to produce is the type of cylinder used for the body portion of a collapsible squeeze tube such as a tooth paste tube, hair cream tube, or the like, having a central aluminum ply and outer thermo-plastic plies.
Basically, the cylinder is formed by wrapping a piece of flexible web material into a cylindrical form and then applying heat along overlapped longitudinal edges to melt or weld together thermo-plastic plies and form a seam or seal, thereby closing the cylinder.
U.S. Pat. No. 3,959,066, which issued May 25, 1976, to the Inventors of the present invention, illustrates a prior method and device for forming a flexible cylinder from multi-ply flexible web material having plastic plies. According to U.S. Pat. No. 3,959,066, briefly, the web material is cut into appropriate segments and then is fed through a longitudinal opening into a pre-form cavity wherein it is rolled approximately 360.degree. into the form of a cylinder. A feed roller at the opening rotates continuously and a spring loaded pressure plate has an edge at the cavity opening which forces the web material against the feed roller to assure continuous feed. After the trailing edge of the segment of the web material has passed the edge of the pressure plate, contact between the feed roller and web material is lost and the seam of the "pre-form" is thus precisely located. Thereafter, the pre-form is longitudinally transferred into a non-conducting cylindrical forming cavity. Heat and pressure are applied to fuse the overlapped seam. Heat is supplied by induction heating through the walls of the forming cavity to the aluminum ply at the overlap area. Pressure is applied by means of an expandible balloon mandrel inside the rolled web material. Finally, after the overlapping edges of the web material have been fused together, the balloon mandrel is collapsed and the resulting product is shrunk slightly by cooling jackets clamped around the forming cavity. The flexible cylindrical tube body is removed from the forming cavity on a removal mandrel that has been inserted into the flexible cylinder. The removal mandrel, like the forming mandrel, is an expandible balloon mandrel. It is slipped in between the cylinder and the deflated forming mandrel and expands to hold and remove the cylinder.
Another disclosure showing method and apparatus over which the present invention is an improvement, is German patent application No. P2739239.8 laid open to public inspection on Apr. 13, 1978. The method disclosed in this German document approaches the formation of a flexible cylinder in a different manner than that disclosed in U.S. Pat. No. 3,959,066, especially, in that neither forming cavities nor expandible mandrels are used. Briefly, an appropriate length piece of flexible web material is cut and then transported to a forming station. At the forming station, the flexible web material is pressed around the bottom half of a cylindrical forming mandrel to form a U-shaped web with equal amounts of web material extending upwardly from each side of the mandrel. In a further step, these upwardly extending portions are formed tightly around the mandrel to complete the cylinder. As the mandrel is non-yielding, the heat sealing device can press downwardly against the mandrel and apply heat along the seam. When the welded seam has cooled, the formed tube is stripped from the mandrel for further processing.
This invention concerns the machine for the making of the cylindrical bodies that are used in flexible collapsible tubes. A major object of the invention is to provide such a machine which will operate at a higher speed and which will be less complex and will have fewer parts that require replacement and maintenance. These objectives in turn result in providing a less expensive cylindrical body end product.
It is a related object of this invention to increase the speed of operation of the machine and the through put of fabricated cylindrical bodies by reducing the number of steps required in the fabrication of the tubular body, by simplifying the process of removing the fabricated product from the machine and by reducing reliance on hydraulic arrangements so as to eliminate the lag time involved in the change of state of hydraulic devices.